Method and apparatus for stacking of envelopes or the like

ABSTRACT

Articles, such as envelopes, are formed into stacks that are transported to packing station. For this purpose a stacking and transport mechanism is positioned between a depositing mechanism (4, 4a) and the packing station. Continuously and individually arriving articles are set with one of their edges (6, 6a) on a stacking surface (7, 7a). The articles to be stacked are first held at the beginning of the formation of a stack (10, 10a), by a first, forward or leading stack holder (8, 8a) which moves in the direction in which the stack (10, 10a) increases, (FIG. 4 ) toward the packing station. Thereafter, a second forward or leading stack holder (9, 9a) takes the position of the first, forward stack holder (8, 8a) (FIG. 6 ). Upon completion of the stack (10, 11 or 10a, 11a) (FIG. 2 ) a third, forward or leading stack holder (12, 12a) and a rear stack holder (13, 13a) take over the stack (11, 11a) to transport it to the packing station, whereby simultaneously with the take-over of the stack (11, 11a) by the third forward stack holder (12, 12a) and by the rear stack holder (13, 13a), the first forward stack holder (8, 8a) together with the rear stack holder (13, 13a) operate for separating the completed stack (11, 11a) from the next stack being formed.

FIELD OF THE INVENTION

The invention relates to a method and to an apparatus for stacking thatis, for forming, holding, separating, and transporting of stacks,especially stacks made up of letter envelopes or the like downstream ofa depositing mechanism which deposits continuously and individuallyarriving letter envelopes with one envelope edge on a stacking surface.

BACKGROUND INFORMATION

A method and an apparatus of the type mentioned are known. The apparatushas a forward stack holder and a rear stack holder, whereby the forwardstack holder functions as a holding element during the stack formationwhile the rear stack holder separates the completed stack from the nextstack. The rear stack forms together with the forward stack a transportunit. This known apparatus functions basically in a satisfactory manner.

SUMMARY OF THE INVENTION

The invention aims at solving the problem of further improving thistechnology and to make it more efficient, specifically to assure apositive control of stacks being formed and of an already formed stack.For this purpose the invention provides that during the removingtransport of one stack and the simultaneous formation of the next newstack, simultaneously several stack holders are operational and arebeing moved into the movement path of the stack and out of the movementpath as well as alongside the movement path.

Contrary to the prior art, the invention provides not only two stackholders that simultaneously function as transport unit, rather, theinvention provides further movable stack holders. These further stackholders are, just as the stack holders serving as a transport unit,movable into the motion or movement path of the stack and out of thestack movement path as well as alongside the movement path of the stack.The movement of stack holders along the movement path is limited only tothe area of the stack formation. The stack holders that are only movablein the area of the stack formation are further effective until theirfunction is taken over by the two other stack holders that servesimultaneously as a transport unit.

According to one example embodiment, three stack holders are moved fromone side across the movement path and alongside the movement path of thestack while a fourth stack holder is moved from a second side into themovement path and out of the movement path as well as temporarily alongthe movement path during the stack formation. Due to this combination ofmoving stack holders, the motion of the three stack holders takes placepreferably from below upwardly as well as back and in the longitudinaldirection of the motion path, while the motion of the single stackholder takes place from above downwardly and back as well as in thedirection of the motion path of the stacks.

Since the stack holders become effective partially simultaneously andpartially in alternation, and since they supplement each other inpositively controlling the stacks, a continuous motion sequence ispossible without interruption, whereby the stack formation also takesplace continuously and with an altogether small individual velocity ofthe individual components. As a result, a high degree of operationalreliability and hence a small susceptibility to trouble.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail in the following withreference to example embodiments shown in the accompanying drawing,wherein:

FIG. 1 is a schematic side view of the present apparatus for stackingshowing a partially completed stack;

FIG. 2 is a view as in FIG. 1 but with a completed stack and with stackholders forming a transport unit in a position prior to taking over thecompleted stack;

FIG. 3 is a view as in FIG. 2, showing the stack holders forming thetransport unit after they have taken over the completed stack;

FIG. 4 is a view as in FIGS. 1 to 3, with a completed stack beingtransported away and with a further stack being formed anew;

FIG. 5 is a view as in FIGS. 1 to 4, showing the finished stackcompletely transported away and the further stack still in its state ofbeing formed, whereby the stack is only held by its first forward stackholder;

FIG. 6 is a view similar to FIG. 5 showing the stack being formed, heldby the second forward stack holder;

FIG. 7 is a view similar to FIG. 6, whereby the stack being formed isheld by its second forward stack holder, while the other stack holdersare in a withdrawn waiting position out of which they move into a readyposition;

FIG. 8 shows, on an enlarged scale compared to FIG. 1, a side view ofthe mounting and of the drive of the second forward stack holder;

FIG. 9 shows details of the second forward stack holder;

FIG. 10 is a plan view of the mounting of the first forward stack holderand of the rear stack holder;

FIG. 11 is a side view of the first forward stack holder and of the rearstack holder;

FIG. 12 shows, on a larger scale, details of the mounting of the firstforward stack holder;

FIG. 13 is a view as in FIG. 5 of a modified embodiment; and

FIG. 14 is a view as in FIG. 6 of the embodiment according to FIG. 13.

DETAILED DESCRIPTION OF PREFERRED EXAMPLE EMBODIMENTS AND OF THE BESTMODE OF THE INVENTION

A stacking machine 1 for stacking of letter envelopes 3 coming, forexample, from a feeding station 2, comprises according to FIG. 5 adepositing mechanism 4 having compartment disks 5. The feeding station 2and the depositing mechanism 4 are basically known and not part of theinvention.

As further shown in FIG. 5, the continuously and individually arrivingletter envelopes 3 are deposited with one of their edges 6 by thedepositing mechanism 4 on a stacking surface 7 of the stacking machine1, where, the envelopes are held initially by a first forward stackholder 8. The term "forward" stack holder 8 means that this stack holder8 is located forward in the direction of the stack formation, that is inthe direction of the arrow a in FIG. 5.

As soon as the stack 10 has reached a predetermined size (FIG. 6), asecond forward stack holder 9 takes up the position of the first forwardstack holder 8 and holds the stack being formed so that the firstforward stack holder 8 can be moved out of the movement path of thestack 10 being formed. This is also shown in FIG. 6.

When, finally, the stack 10 being formed has become a complete stack 11according to FIG. 2, the third forward stack holder 12 and a rear stackholder 13, as viewed in the transport direction, take over the stack 11.The two stack holders 12 and 13 form together a transport unit andtransport the completed stack 11 out of the zone of the stack formation,for example, to a turnover and packaging station 14 as is shown in FIGS.2 to 5 or 6.

When the two stack holders 12 and 13 serving as a transport unit takeover the stack 11, the first forward stack holder 8 is simultaneouslymoved in front of the next part to be stacked. Thus, the first forwardstack holder 8 serves simultaneously as a separation element between afinished, completed stack 11 and the next stack 10 being formed (FIGS. 2and 3).

For the forming, holding, separating, and transporting of stacks 10, 11there are thus several, more specifically four stack holders 8, 9 and12, 13 for positively controlling the stacks. These holders move intothe motion path of the stacks 10, 11 and out of the motion path of thestacks. Additionally, the holders move alongside the motion path of thestacks 10, 11. Three stack holders 8, 12, and 13 move from one sideacross the motion path of the stacks 10, 11, and alongside of the motionpath, whereas the fourth stack holder 9 moves from a second side intothe motion path and out of the motion path again. At certain timesduring the stack formation the fourth holder 9 also moves alongside themotion path.

According to the example embodiment shown in FIGS. 1 to 7, the secondforward stack holder 9 is tilted from above in front of a stack beingformed, and moves during the stack formation along the motion path ofthe stack 10 until the stack holder is tilted again upwardly and thenmoves backward in the direction of the depositing mechanism.

The individual figures show the different process steps as follows.

According to FIG. 1, the second forward stack holder 9 holds the stack10 being formed while the stack holders 12 and 13 serving as a transportunit are in a ready position. At this time the first forward stackholder 8 is also in its ready position. In this ready position, thestack holders 8 and 13 are located with a slight spacing in front of thestack 10 on its side facing the depositing mechanism 4 and extend withtheir free ends 16 slightly above the stack surface 7.

In FIG. 2, the stack 11 has reached its full size. The second forwardstack holder 9 and the third forward stack holder 12 that forms part ofthe transport unit, are positioned in one plane. The rear stack holder13 and the immediately next to it located first forward stack holder 8have moved out of the ready position of FIG. 1 into contact with thelast member 15 of the complete stack 11. This operation takes place on arelatively low level so that initially, the forward stack holder 12, aswell as the rear stack holder 13, rest against the outside of the stack11 only with their upper edges 16.

As shown in FIG. 3, then the two stack holders 12 and 13 move along thestack upwardly and simultaneously somewhat in the movement direction ofthe stack 11 to be transported away.

The stack 10 or 11 rests in the stack formation area suitably on theupper run of a conveyor belt 17 running around guide rollers 18 to 23and around one driving and guide roller 24.

The transport speed of the two stack holders 12 and 13 forming thetransport unit is larger than the transport speed of the conveyor belt17 so that quickly a gap 25 is formed relative to the next stack 10being formed (FIG. 4). This next stack 10 being formed is held by thefirst forward stack holder 8 which has been moved together with the rearstack holder 13 out of the ready position according to FIG. 1 aftercompletion of the stack 10 according to FIG. 2, into contact with thelast member 15 of the stack, whereby this movement initially also takesplace on a low level. Thereafter, the first forward stack holder 8 ismoved crosswise to the stack direction out of the position of FIG. 2into the support position of FIG. 3. Further, when the third forwardstack holder 12 has reached its upper position of FIG. 3, the secondforward stack holder 9 is moved out of the motion path of the stack 11.At this stage, the stack holder 9 tilts out of the motion path of thestack 11 (FIG. 4).

According to FIG. 5 the two transport stack holders 12 and 13 havereached with the stack 11 the turnover and packaging station 14. Duringthis time, the stack 10 being formed has grown in size.

FIG. 6 shows the situation in which the turnover and packaging station14 has taken over the stack 11 by its turnover fork 26. Further, afolding box has already been pushed over the stack 11. Thus, the stackholders 12 and 13 serving as a transport unit, can release themselvesfrom the stack 11. For this purpose, they are pulled away from thestack. This takes place according to the example embodiment downwardlyby lowering the two stack holders 12 and 13.

However, prior to the lowering of the holders 12, 13, the second forwardstack holder 9 which is tiltable inwardly from above has taken over thesecuring of the stack being formed as shown by comparing of FIGS. 5 and6. With the lowering of the two stack holders 12 and 13, the firstforward stack holder 8 is also lowered according to the exampleembodiment so that it can no longer hold the stack being formed (FIG.6).

Thereafter, the three stack holders 8, 12, and 13 that are movable fromthe same side across the motion path of the stacks 10, 11 move from theposition on the left side of FIG. 6 into a waiting position on the rightside in FIG. 7. In this waiting position, the free end 16 of the stackholders 8, 12, and 13 are still below the stacking surface 7 at a levelinto which they are moved back after the lowering shown in FIG. 6 into aposition according to FIG. 7. From this lowered level below the stackingsurface 7, the stack holders 8, 12, and 13 are then lifted again intothe ready position until they extend with their upper free end 16somewhat above the level of the stacking surface 7 as is shown inFIG. 1. Thereafter, the above described process steps will be repeated.

A mechanism 30 serves for mounting and driving the first forward stackholder 8 and the stack holders 12 and 13 serving as a transport unit.The mechanism 30 can be lowered with the aid of a stroke device 31 shownonly symbolically in the figures, said lowering taking place from thelifted position of FIG. 1 into the position of FIG. 6. The mechanism 30comprises components for mounting and guiding, as well as driving thestack holders 8, 12, and 13.

The first forward stack holder 8 and the two stack holders 12 and 13forming a transport unit are each arranged on a slide 32 or 33 and 34(FIG. 1). The mechanism 30 according to the example embodiment comprisesoutwardly positioned guide rods 35 and 36 (FIG. 10) for mounting andguiding the slides 32 of the stack holder 8. The mechanism 30 furthercomprises inwardly located guide rods 37 and 38 for mounting and guidingthe two other stack holders 12 and 13, whereby in FIG. 10 only the slide33 with the stack holder 13 is shown, while the slide 34 with the stackholder 12 is not also shown. The pairs of guide rods 35, 36, as well as37 and 38 are located preferably at different elevations as is seen inFIG. 11.

The rear stack holder 13 and the first forward stack holder 8 whichfunctions with the rear stack holder 13 as a separation element,comprise each, for example, four elongated finger type elements 39 or40, which form in turn with the aid of angle irons 41 and 42, and guidebushings 43 or 44 the slides 32 and 33 according to FIGS. 10 and 11. Theguide bushings 43 or 44 are mounted on guide rods 35 to 38 at the endsof the angle irons 41 and 42.

Further, an electromagnetic clutch 45 is secured to the slide 32 withthe aid of a bracket 46 as shown symbolically in FIGS. 10 and 12. Theslide 33 of the rear stack holder 13 carries a steel plate 47 (FIG. 12)provided for the electromagnetic clutch 45. The two slides 32 and 33 arethus temporarily connected to each other by the holding force of theelectromagnetic clutch 45.

The connection of the two slides 32 and 33 and thus the synchroneousmovement in unison of the rear stack holder 13 and of the first forwardstack holder 8 which simultaneously forms therewith a separationelement, is important when these stack holders 8 and 13 are moved veryrapidly out of the ready position according to FIG. 1 into theseparating position according to FIG. 2. Such movement is approximatelyinstantaneous, whereby this movement must take place exactly between twoparts to be stacked. Upon reaching the separation position according toFIG. 2, the two stack holders 8 and 13 still move in unison crosswise tothe motion path of the stack 11. However, now a separation of the twostack holders 8 and 13 takes place. The stack holders 13 must only holdstill the completed stack 11 during its transport to the turnover andpackaging station 14, while the first forward stack holder 8 preventsfalling over of the next envelopes deposited by the depositing mechanism4.

The release of the two slides 32 and 33 within the operating range oftheir electromagnetic clutch 45 for separating the two stack holders 8and 13 from each other, takes place with the aid of switches which arenot shown in the Figures, and which may be controlled by the slidesthemselves.

The mechanism 30 further comprises a piston cylinder unit 47 which may,for example, be a cylinder without a piston rod, the piston of which,which is not shown in the Figures, moves the two stack holders 8 and 13instantaneously out of the waiting position according to FIG. 1, intothe separation position according to FIG. 2. The free ends 16 of the twostack holders 8 and 13 are located in the waiting position according toFIG. 1, already within the radius of the compartment disk 5 in the planeof the deposit support 48 of the depositing mechanism 4 as also shown inFIG. 1. Additionally, the mechanism 30 is slightly lifted by the strokedevice 31.

The transport of the stack 11 out of the position of FIG. 2 or 3 all theway to the turning and packaging station 14 takes place with the aid ofthe piston cylinder device 47 which is connected with the rear stackholder 13 to displace the same.

The piston cylinder device 47 moves the rear stack holder 13 back againinto the starting position or waiting position according to FIG. 7,whereby the slide 32 of the first front stack holder 8 is coupled withthe slide 33 of the rear stack holder 13 with the aid of theelectromagnetic clutch 45. The stack holder 12 belonging to thetransport unit receives its drive for the rearward motion from a returnspring which is not shown in the figures for clarity's sake.

A gear belt 51 (FIGS. 10 and 11) is provided for the slide 32 of thefirst forward stack holder 8. The gear belt 51 is driven synchroneouslywith the conveyeor belt 17 (FIG. 3). This gear belt 51 is coupled withthe slide 32 or decoupled therefrom by a clamping cylinder of apneumatic clutch 52. This is necessary because the slide 32 istemporarily coupled through the electromagnetic clutch 45 with the slide33, which then moves the slide 32.

The gear belt 51 is guided with the aid of a guide roller 53 at the freeend 54 of the mechanism 47 (FIG. 1), and further runs over the guiderollers 55 and 56 which are mounted on the piston cylinder device 47 orwhich are elevationally adjustable together therewith. Further, the gearbelt 51 is guided over the guide rollers 57 and 58 which are mounted ona carrier and guide device 59 (FIG. 1) for the mechanism 30 with thepiston cylinder device 47.

For the tilting and horizontal movement of the second forward stackholder 9, which is tiltable from above into a position in front of thestack 10 being formed, there is provided a guide and holding mechanism60, the essential details of which are shown in FIGS. 8 and 9.

The stack holder 9 comprises, just as the stack holder 12, several,preferably four elongated, finger-type elements 61 which are arranged ona carrier 62. The elements 61 and the carrier 62 are tiltably mounted onarms 63 of a slide 64 for tilting about an axis 65. The slide 64 isdisplaceable along guide rods 66 which are part of the guiding andholding mechanism 60.

A gear belt 69 is provided for driving the slide 64, one end of whichruns around a drive wheel 67 and which is guided around a guide wheel68. The gear belt 69 can be coupled or decoupled from the slide 64. Forthis purpose, again a pneumatic clutch 70 is provided which is onlyschematically indicated at the slide 64 in FIG. 8. The gear belt 69 is,in principle, driven in synchronism with the conveyor belt 17 so that arelease from the gear belt 69 is necessary when the stack holder 9 orthe slide 64 carrying the stack holder 9 are being moved back into thestarting position according to FIGS. 4 and 5.

A roll up spring 71 is provided for pulling back the slide 64. The rollup spring 71 is connected with its one end 72 in the area of the drivewheel 67 to the guiding and holding mechanism 60 and is further guidedaround a roll up spring drum 73 which is mounted on the slide 64.

A tilting cylinder 74 serves for tilting the stack holder 9. A pistonrod 75 of the cylinder 74 is pivoted to an arm 76 of the carrier 62. Asecond arm 77 serves as a carrier for the tilting cylinder 74 andconnects the latter with the slide 64.

The guiding and holding mechanism 60 further comprises an upper stackguide element 80 (FIGS. 1, 8) which is carried by guide rods 81 that arevertically adjustable. The finger-type element 61 of the stack holder 9reach through the stack guide element 80.

FIGS. 13 and 14 show a modified apparatus 1aof the invention forstacking or rather forming, holding, separating, and transporting ofstacks 10a or 11a, whereby the same reference numbers serve fordesignating the same components, however with the index a.

The apparatus 1a of FIGS. 13 and 14 differs from the stacking machine 1described first, only in that the second stack holder 9a on a slide 64ais not tiltable, rather it is movable perpendicularly to the stackingsurface 7a. The second forward stack holder 9a is mounted for movementin a vertical direction and it is further displaceable with the aid ofthe slide 64a parallel to the stack 10a as the latter grows in size.

The mounting and the drive for the slide 64a in the guiding and holdingmechanism 60a may in principle be constructed exactly as described withreference to the first example embodiment. A difference thus exists onlyas far as the slide 64a carries a stroke mechanism 90a, for example, inthe form of a piston cylinder device by means of which the secondforward stack holder 9a is lifted when necessary as is shown in FIG. 13or is lowered as is shown in FIG. 14. The slide 64a comprises for thispurpose, a carrier 91a extending upwardly. The piston cylinder device90a is connected to the upper end of the carrier. An entraining dog 93aconnects the free end of the piston rod 92a with the second forwardstack holder 9a. Preferably, the piston rod is guided and supported inthe slide 64a.

The function and operation of the guiding and holding mechanism 60a withthe second forward stack holder 9a that is movable parallel andvertically relative to the stacking surface 7a does not differ from thatof the first described example embodiment when cooperating with thefirst forward stack holder 8a and the two other stack holders 12a or13a. As long as the stack holder 8a according to FIG. 13 holds the stack10a, the stack holder 9a is in a lifted position. When the two stackholders 12a and 13 release the stack 11a and are lowered for thispurpose, the stack holder 8a also releases the stack 10a newly beingformed, because it is lowered together with the two other stack holders12a and 13a. Simultaneously, the stack holder 9a takes over the functionof holding the stack 10a. For this purpose, the piston cylinder deviceor stroke mechanism 90a shifts the stack holder 9a in front of the stack10a as is shown in FIG. 14.

The three stack holders 8, 12, and 13 or 8a, 12a and 13a move in unisonrespectively in a vertical direction or perpendicularly to the stackingsurface 7 or 7a and in the horizontal direction only partially inunison, namely when especially the two stack holders 8 and 13 or 8a and13a are moving out of the waiting position according to FIG. 7 into theready position according to FIG. 1 and then through the separationposition according to FIG. 2 into the transport and take over positionaccording to FIG. 3. During the subsequent motion sequences until thewaiting position is reached, the stack holders 8, 12, and 13 or 8a, 12a,and 13a move substantially independently of one another.

Although the invention has been described with reference to specificexample embodiments, it will be appreciated that it is intended to coverall modifications and equivalents within the scope of the appendedclaims.

It is claimed:
 1. A method for forming, holding, separating, andtransporting stacks (10, 10a; 11, 11a) of articles (3, 3a) downstream ofa depositing mechanism (4, 4a) which deposits continuously andindividually arriving articles with an article edge (6, 6a) on astacking surface (7, 7a) to form said stacks, said transporting takingplace in a transport direction (a) from said depositing mechanism to apacking station (14), said stack having several sides extending inparallel to said transport direction, said method comprising thefollowing steps:(a) first holding articles at the beginning of a stackformation by a first leading stack holder (8, 8a) which moves in saidtransport direction in which a stack size increases; (b) second holdinga partly formed stack by a second leading stack holder (9, 9a) whichtakes over said partly formed stack from said first leading stack holder(8, 8a) while said second leading stack holder (9, 9a) is also moving insaid transport direction; (c) engaging a leading end of a completedstack (11, 11a) by a third leading stack holder (12, 12a) and engaging arear end of said completed stack by a rear fourth stack holder (13, 13a)for further transporting said completed stack (11, 11a) in saidtransport direction (a) toward said packing station (14); (d)simultaneously with said engaging of the completed stack (11, 11a) bysaid third leading stack holder (12, 12a) and by said rear fourth stackholder (13, 13a), separating said completed stack (11, 11a) from a nextstack (10) being formed, by entering said first leading stack holder (8,8a) and said rear fourth stack holder (13, 13a) between said completedstack (11, 11a) and said next stack (10, 10a); (e) supporting said nextstack by said first leading stack holder (8, 8a) and by said rear fourthstack holder (13, 13a); (f) moving any three stack holders (8, 8a; 12,12a; 13, 13a) of said four stack holders crosswise to said transportdirection (a) from one stack side of said several sides of said stackand also moving said any three stack holders alongside said transportdirection for said transporting of a stack; and (g) moving any one stackholder (9, 9a) of said four stack holders crosswise to said transportdirection from another stack side and also moving said any one stackholder (9, 9a) temporarily in said transport direction and then oppositesaid transport direction back to a starting position.
 2. The method ofclaim 1, wherein any two of said three leading stack holders and saidrear stack holder form said any three stack holders for performing saidmoving of said step (f); and wherein said any one stack holder (9, 9a)is the third of said three stack holders for performing said moving ofsaid step (g).
 3. The method of claim 1, further comprising forming atransport unit of said rear stack holder (13, 13a) and of one (12, 12a)of said three leading stack holders, sequentially operating the othertwo leading stack holders (8, 8a; 9, 9a) for holding a next stack beingformed until the next stack is complete, and then moving said transportunit (12, 12a; 13, 13a) to take over a completed stack and to bring saidcompleted stack to said packing station (14).
 4. An apparatus forforming, holding, separating and transporting stacks of articles (3, 3a)downstream of a depositing mechanism (4, 4a) which deposits continuouslyand individually arriving articles with an article edge, comprising astacking surface (7, 7a) leading in a transport direction from saiddepositing mechanism (4, 4a) to a packing station (14), said stackingsurface forming a stacking level on which articles are deposited, saidapparatus further comprising four movable stack holders for holding anarticle on said stacking surface, drive means connected to said fourstack holders for operating said stack holders, said movable stackholders comprising three leading stack holders (8, 9, 12 or 8a, 9a, 12a)and one rear stack holder (13, 13a), said drive means comprising firstdrives adapted for moving said three leading stack holders crosswise ofsaid transport direction (a) and in parallel to said transportdirection, said drive means further comprising a second drive adaptedfor moving said rear stack holder (13, 13a) crosswise of said transportdirection and in said transport direction for holding a stack during itsformation and for transporting a completed stack, said first drives, twoof said three leading stack holders (8, 8a; 12, 12a), and said rearstack holder (13, 13a) being arranged for moving said two leading stackholders and said rear stack holder from one and the same side of a stackcrosswise to said transport direction and in parallel to said transportdirection, and wherein said second drive and the third of said threeleading stack holders are arranged for moving from another side of astack crosswise to said transport direction and in parallel to saidtransport direction, whereby a stack is positively held and guidedduring its formation and during its transportation.
 5. The apparatus ofclaim 4, wherein three of said four stack holders (8, 12 and 13 or 8a,12a and 13a) are mounted below said stacking surface (7, 7a), andwherein one stack holder (9, 9a) of said four stack holders is mountedabove a stack (10, 11 or 10a, 11a).
 6. The apparatus of claim 5, whereinsaid one stack holder (9) mounted above the stack (10, 11) is supportedin a tiltable manner crosswise to said transport direction and in aslidable manner in said transport direction.
 7. The apparatus of claim5, wherein said three stack holders (8, 12 and 13 or 8a, 12a and 13a)mounted below said stacking surface are mounted on slides (32, 33, 34)movable in said transport direction, said first drive comprising astroke mechanism (31) for moving said three stack holders in unisoncrosswise to said transport direction.
 8. The apparatus of claim 4,wherein one stack holder (9, 9a) of said three leading stack holders istiltable from above into a position in front of a stack being formed,said tilting being directed toward another leading stack holder (8, 8a)that is movable from below said stacking surface in front of the stack(10, 10a), said one stack holder being also movable during a stackformation alongside said transport direction, said one stack holder (9,9a) being further tiltable upwardly and then movable opposite saidtransport direction toward said depositing mechanism (4, 4a).
 9. Theapparatus of claim 4, wherein one stack holder (9a) of said threeleading stack holders is movable parallel and vertically relative tosaid stacking surface (7a).
 10. The apparatus of claim 4, wherein saidfirst leading stack holder (8) and said rear stack holder (13) aremovable into and out of a travel path of a stack in synchronism witheach other.